The invention relates to an assembly for the hydraulic actuation of equipment for particular use in hydrocarbon extraction, such as crude oil or natural gas extraction. Such equipment may be, for example, a safety valve in fluid communication with a riser or a Christmas tree used in hydrocarbon extraction from subsea wells. The assembly comprises a pump device that includes a piston/cylinder unit and an electrical drive device which is movably connected to a piston of the piston/cylinder unit for intermittent pump movement. The pump device is disposed between a fluid feed line and a supply line communicating with the equipment.
Such a pump device is known from DE 20.3 11 03.3 and PCT/EP2004/007948, hereby incorporated herein by reference. A pump device as such comprises a screw drive, a reduction gear unit, a spurwheel gear unit and at least one drive shaft with at least one electric motor driving the drive shaft. The screw drive comprises a rotatable, but axially immovable spindle nut, and an axially movable threaded spindle which is connected at an actuating end to the piston of the piston/cylinder unit. The appropriate reduction gear unit can, for example, be a so-called harmonic drive gear unit.
The piston is movably supported in a piston cavity of a cylinder of the piston/cylinder unit, wherein the piston cavity includes at least one suction hole and one discharge hole; and non-return or check valves subject to force can be arranged in each of these holes in different directions.
A discharge hole or a discharge line, which leads to a pressure switch, can branch from the supply line. This can actuate a safety valve. An electrical servomotor can be provided to actuate the safety valve.
Reference is made to DE 203 11 033 for the further description of the pump device.
It may be desirable on site, which also means below the surface of the sea, to bypass the pump device in a simple manner in an emergency in order to be able to continue to feed hydraulic fluid with an adequate pressure to the appropriate equipment, such as a subsea safety valve.